The present invention relates to a semiconductor light-emitting device, and more particularly, to a semiconductor light-emitting device that suppresses characteristic deterioration.
Semiconductor light-emitting devices such as light emitting diodes (LEDs) and semiconductor laser diodes (LDs) are incorporated and used in various devices. The use of nitride semiconductor light-emitting devices having excellent characteristics has advanced in recent years. As an example of such nitride semiconductor light-emitting devices, an inner stripe type nitride semiconductor laser diode having a current block layer made of AlN is proposed (Japanese Unexamined Patent Application Publication No. 2003-78215).
A semiconductor laser 300 serving as an inner stripe type nitride semiconductor laser diode disclosed in Japanese Unexamined Patent Application Publication No. 2003-78215 will be described below. FIG. 7 is a sectional view schematically showing the configuration of the semiconductor laser 300 serving as the inner stripe type nitride semiconductor laser diode disclosed in Japanese Unexamined Patent Application Publication No. 2003-78215.
The semiconductor laser 300 has a configuration in which an Si-doped n-type GaN layer 302 (Si concentration: 4×1917 cm−3; thickness: 1 μm), an n-type cladding layer 303, an n-type optical confinement layer 304, a 3-period multiple quantum well (MQW) layer 305, a cap layer 306, and a p-type GaN guide layer 307 are stacked on an n-type GaN substrate 301. The n-type cladding layer 303 is made of Si-doped n-type Al0.1Ga0.9N (Si concentration: 4×1017 cm3; thickness: 2 μm). The n-type optical confinement layer 304 is made of Si-doped n-type GaN (Si concentration: 4×1017 cm−3; thickness 0.1 μm). The 3-period multiple quantum well (MQW) layer 305 is composed of an In0.15Ga0.85N (thickness: 3 nm) well layer and an Si-doped In0.01Ga0.99N (Si concentration: 1×1018 cm−3, thickness: 4 nm) barrier layer. The cap layer 306 is made of Mg-doped p-type Al0.2Ga0.8N. The p-type GaN guide layer 307 is made of Mg-doped p-type GaN (Mg concentration: 2×1019 cm−3; thickness: 0.1 μm).
A current constriction layer 308, a p-type cladding layer 309, and a contact layer 310 are stacked on the p-type GaN guide layer 307. The current constriction layer 308 corresponds to the above-mentioned current block layer. The p-type cladding layer 309 is made of Mg-doped p-type Al0.1Ga0.9N (Mg concentration: 1×1019 cm−3; thickness 0.5 μm). The contact layer 310 is made of Mg-doped p-type GaN (Mg concentration: 1×1020 cm−3; thickness: 0.02 μm). A p-type electrode 311 is formed on the upper surface of the contact layer 310, and an n-type electrode 312 is formed on the lower surface of the n-type GaN substrate 301.
The current constriction layer 308 has an opening 308a. The p-type GaN guide layer 307 and the p-type cladding layer 309 contact each other via the opening 308a. In the semiconductor laser 300, a contact width between the p-type electrode 311 and the contact layer 310 can be set to be greater than the width of the opening 308a. Therefore, even when the opening 308a has a narrow width of about 1 to 2 um for allowing a horizontal mode control, a low contact resistance is obtained. As a result, a semiconductor laser having a low device resistance can be achieved.
The opening 308a is formed by performing wet etching on the current constriction layer 308 which is an AlN layer grown at a low temperature. This provides an advantage that damage or impurity contamination caused during formation of the opening 308a has less adverse effect. Accordingly, the semiconductor laser 300 is expected as a high-output semiconductor laser with low-voltage operation.
Further, a technique for facilitating device isolation of a nitride semiconductor device is proposed (Japanese Unexamined Patent Application Publication No. 2008-135785). In this technique, after formation of groove portions in a semiconductor wafer on which a nitride semiconductor is formed, break lines are formed by a laser scriber within the groove portions, and the wafer is divided into nitride semiconductor devices along the break lines. Note that related arts are disclosed (Japanese Unexamined Patent Application Publication Nos. 2001-68786 and 07-22690).